The invention relates to a method for detecting target objects and for determining their direction, range, speed and the like for a radar device.
As disclosed, for example, in EP 0 727 051 B1, radar technology has become important for use in the motor vehicle industry to the extent that safety standards for a motor vehicle must be continuously adapted as the traffic density becomes ever greater. Radar devices have been designed to detect both stationary target objects and target objects moving relative to a motor vehicle, without making any contact with them. These devices can determine their range, speed, condition, presence, direction, etc. The radar devices used for this purpose are essentially based on two main traffic techniques relating to radar technology, which are known by the names xe2x80x9csimultaneous lobingxe2x80x9d and xe2x80x9csequential lobingxe2x80x9d.
The term xe2x80x9csimultaneous lobingxe2x80x9d means a monopulse radar technique. The radar devices used to implement this technique and which use this technique include a transmitting and receiving device having typically 2 (one-dimensional) or 4 (two-dimensional) detection areas, which partially overlap and are evaluated simultaneously. The aim is to obtain an accurate measurement of the position angle of the target object with respect to the radar device axis by means of intensity comparison. Angular resolution is not feasible, that is to say two or more objects at the same distance cannot as such be resolved separately from one another, since only a single object is detected rather than the at least two objects and, furthermore, this object is associated with an incorrect position angle.
The radar technique of xe2x80x9csequential lobingxe2x80x9d means the production of a number of beams with different beam fields and activation and evaluation of these beams at different times. The angular accuracy achieved in this way does not satisfy stringent demands for accurate measurement of the position angle of the target object, for use in motor vehicles. This is primarily due to the fact that, in this method, fluctuation errors which occur to a considerable extent have a very major influence on the measurement of the position angle, so that the measurements are subject to considerable intensity fluctuations. This can lead, inter alia, to misinterpretations of the position angle change when the signals are evaluated.
The document U.S. Pat. No. 5,598,163 discloses a multibeam radar system, which has a number of transmitting and receiving devices. The detection area of the radar system in this case comprises the beam fields of the receiving devices. The echo signals are in this case evaluated using the monopulse method.
In one embodiment of the invention, there is a method for detecting target objects using a radar device, including arranging at least three transmitting and receiving devices for radar beams such that their beam fields form a detection area of the radar device; activating and deactivating the at least three transmitting and receiving devices such that at least two adjacent transmitting and receiving devices are operated simultaneously, and evaluating the echo signals from the transmitting and receiving devices using the monopulse method.
In one aspect of the invention, one pair of adjacent transmitting and receiving devices are activated simultaneously.
In another aspect of the invention, at least one of the currently deactivated transmitting and receiving devices is reactivated for activation of the at least two transmitting and receiving devices.
In yet another aspect of the invention, the echo signals from the transmitting and receiving devices are evaluated individually on the basis of range, speed and intensity.
In still another aspect of the invention, the position angle of the target object relative to the radar device is determined by comparison of the intensities of the at least two transmitting and receiving devices.